Problem: Evaluate the following expression. $6\div 3+9^2-4 =$
Solution: $\begin{aligned} &\phantom{=}6\div 3+9^2-4 \\\\ &=6\div 3+(9\cdot 9)-4 \end{aligned}$ $=6\div 3+81-4$ $=2+81-4$ $=83-4$ $=79$